Contaminants Research

Today, our nation's drinking water supply is one of the cleanest in the world, in part because EPA has set standards for about 90 contaminants that can affect drinking water. Even so, microbes, chemicals, and pathogens are still a concern.

Microbes

Microbes are tiny organisms that are all around us, including in our water, and they are capable of causing diseases in humans. Waterborne diseases killed thousands of people around the world before water treatments, such as disinfection and filtration, were developed. Microbes that cause waterborne diseases include bacteria, which can cause cholera and typhoid; viruses, which can cause polio, hepatitis, and various gastrointestinal diseases; and protozoa, which can cause giardiasis and cryptosporidiosis.

EPA is pursuing several research areas that address microbes in drinking water:

• Microbial source tracking
• Disinfection and pathogens on the Candidate Contaminant List (a list of drinking water contaminants to be considered for future regulation)
• Wastewater biosolids
• Techniques to detect and remove or inactivate microbial contaminants
• Methods of disinfection

Chemicals

EPA’s research on chemical contaminants focuses on sources of suspected endocrinedisrupting chemicals (EDCs) that impact the environment, the risks posed by the use of pesticides, the effect of personal care products on our drinking water, and balancing the risks from microbial pathogens in our drinking water against the risks of creating disinfection by-products.

Scientists are also looking at emerging chemical contaminants; they are of increasing regulatory interest. They may be currently unregulated or may be subject to new or revised regulatory standards. Characteristically, they occur at low levels, enter the aquatic environment from multiple sources, and are considered a long-term issue (not an issue that requires emergency action). Some of these chemicals may have harmful estrogenic (hormonal) effects on both wildlife and humans.

Monitoring for contaminants of interest is conducted at selected drinking water utilities, and chemical analyses are performed by the utilities or by commercial laboratories. EPA determines the extent of occurrence and the risk posed to the public via drinking water. This will ultimately lead to an appropriate EPA action for that chemical contaminant—regulation, guidance, or a decision not to regulate.

Pathogens

Pathogens are small life forms that can cause disease. They’re often found in water as a result of sewage discharges that contain fecal matter, leaking septic tanks, and runoff from animal feedlots. EPA develops scientific assessments that lead to protection from exposure to harmful levels of pathogens in drinking water.

Pathogens are microorganisms such as bacteria, fungi, protozoa, and viruses. One microorganism of concern is Cryptosporidium. This protozoan parasite enters our source water through sewage and animal waste. It causes cryptosporidiosis, a mild gastrointestinal disease. EPA regulates Cryptosporidium in our drinking water by requiring at least 99 percent of Cryptosporidium protozoa be removed by filtered surface water systems serving 10,000 people or more.

Giardia lamblia, another troublesome pathogen, also infects the gastrointestinal tract. It causes giardiasis. Waterborne giardiasis may occur as a result of disinfection problems or inadequate filtration procedures. EPA regulates Giardia in our drinking water by requiring water systems to disinfect or filter their water so that at least 99.9 percent of Giardia is physically removed or rendered harmless.

Small water distribution systems face unique challenges when it comes to protecting drinking water from Cryptosporidium and Giardia lamblia. So EPA’s pathogens research includes investigating the risk trade-offs with disinfection by-products and ways for small systems to control microbial pathogens.

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